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Centre de recherche Cerveau et Cognition (Toulouse / 1993-....).

Overview
Works: 27 works in 52 publications in 2 languages and 53 library holdings
Roles: Other
Publication Timeline
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Most widely held works by Centre de recherche Cerveau et Cognition (Toulouse / 1993-....).
Visuotopie et traitement du flux optique chez le singe : une investigation par IRMf by Samy Rima( Book )

2 editions published in 2017 in English and held by 2 WorldCat member libraries worldwide

L'imagerie par résonance magnétique fonctionnelle (IRMf) permet d'examiner l'organisation fonctionnelle du cerveau humain de manière non-invasive et chez les sujets sains. L'implémentation de cette technique chez des primates non-humains représente un progrès important dans les neurosciences des systèmes. D'une part, l'IRMf singe permet la réduction et le raffinement des protocoles invasifs impliquant des primates non humains, en révélant les régions d'intérêts dans lesquelles les approches focales invasives, électrophysiologiques ou anatomiques, devraient être menées. D'un autre côté, les connaissances acquises avec ces approches invasives peuvent être transposées plus aisément à l'homme, une fois que les homologies et différences interspécifiques ont été identifiées au travers de protocoles d'IRMf menées en parallèle chez les primates humains et non- humains. La 1ère partie de cette thèse présente les approches conventionnelles d'étude des fonctions cérébrales. Nous montrons que des études invasives chez l'animal demeurent nécessaires pour comprendre les mécanismes neuronaux qui sous-tendent nos fonctions cognitives, malgré le progrès des techniques d'investigation chez l'homme. Suit une revue sur l'évolution des techniques d'IRMf singe et certaines de ses réalisations majeures comme pont dressé entre les études non-invasives menées chez l'homme et les études invasives réalisées chez l'animal, notamment en ce qui concerne notre compréhension des mécanismes neuronaux permettant la saisie manuelle d'objets sous contrôle visuel. Purement méthodologique, la fin de cette 1ère partie décrit l'animalerie et la plate-forme d'IRM à Toulouse et expose les jalons de l'implémentation de l'IRMf chez le singe macaque vigile. La 2ème partie de la thèse présente les 4 études que nous avons menées en IRMf singe. La 1ère étude modélise la réponse hémodynamique chez le singe, un outil indispensable à l'analyses de données d'IRMf, acquises dans les études suivantes. La 2ème étude traite de l'organisation visuotopique du cortex visuel dorsal des primates, et y décrit un nouvel assemblage d'aires visuotopiques chez 2 animaux, grâce à l'usage de nouvelles techniques de stimulation visuelle et d'analyse de champ récepteurs. Ces résultats apportent un point de vue neuf sur l'organisation fonctionnelle de la voie visuelle dorsale et ouvrent de nombreuses perspectives pour les comparaisons entre espèces. La 3ème étude cartographie le réseau d'aires corticales impliqué dans le traitement du flux optique chez les primates non humains et le compare à celui décrit récemment chez l'homme. Grâce à la réplication d'une étude réalisée chez l'homme, nous avons confirmé chez 3 macaques l'implication de zones précédemment identifiées par des enregistrements électrophysiologiques. Nos résultats révèlent de nouvelles zones corticales impliquées dans le traitement du flux optique, dessinant l'image d'un réseau cortical partageant de nombreuses similitudes, mais ayant également des différences frappantes, avec celui documenté dans le cerveau humain. En résumé, l'ambition de cette thèse est double : (1) fournir des recommandations pour la mise en place de techniques IRMf chez le singe, tirées de notre propre expérience et (2) exposer les résultats d'un ensemble d'études que nous avons menées avec cette approche, traitant de l'organisation visuotopique du cortex visuel dorsal et de son implication dans le traitement du mouvement visuel. En plus d'apporter une perspective nouvelle sur l'organisation fonctionnelle du cortex visuel chez les primates non humains, ces études illustrent la contribution de l'IRMf singe comme pont entre études électrophysiologiques chez les primates non humains et études d'imagerie fonctionnelle chez l'homme
Phase entrainment and perceptual cycles in audition and vision by Benedikt Zoefel( Book )

2 editions published in 2015 in English and held by 2 WorldCat member libraries worldwide

Recent research indicates fundamental differences between the auditory and visual systems: Whereas the visual system seems to sample its environment, cycling between "snapshots" at discrete moments in time (creating perceptual cycles), most attempts at discovering discrete perception in the auditory system failed. Here, we show in two psychophysical experiments that subsampling the very input to the visual and auditory systems is indeed more disruptive for audition; however, the existence of perceptual cycles in the auditory system is possible if they operate on a relatively high level of auditory processing. Moreover, we suggest that the auditory system, due to the rapidly fluctuating nature of its input, might rely to a particularly strong degree on phase entrainment, the alignment between neural activity and the rhythmic structure of its input: By using the low and high excitability phases of neural oscillations, the auditory system might actively control the timing of its "snapshots" and thereby amplify relevant information whereas irrelevant events are suppressed. Not only do our results suggest that the oscillatory phase has important consequences on how simultaneous auditory inputs are perceived; additionally, we can show that phase entrainment to speech sound does entail an active high-level mechanism. We do so by using specifically constructed speech/noise sounds in which fluctuations in low-level features (amplitude and spectral content) of speech have been removed, but intelligibility and high-level features (including, but not restricted to phonetic information) have been conserved. We demonstrate, in several experiments, that the auditory system can entrain to these stimuli, as both perception (the detection of a click embedded in the speech/noise stimuli) and neural oscillations (measured with electroencephalography, EEG, and in intracranial recordings in primary auditory cortex of the monkey) follow the conserved "high-level" rhythm of speech. Taken together, the results presented here suggest that, not only in vision, but also in audition, neural oscillations are an important tool for the discretization and processing of the brain's input. However, there seem to be fundamental differences between the two systems: In contrast to the visual system, it is critical for the auditory system to adapt (via phase entrainment) to its environment, and input subsampling is done most likely on a hierarchically high level of stimulus processing
Prior knowledge contribution to declarative learning : a study in amnesia, aging and Alzheimer's disease by Pierre-Yves Jonin( Book )

2 editions published in 2019 in French and held by 2 WorldCat member libraries worldwide

The experimental study of human memory has had two historic moments in the last sixty years. 1957 marks the discovery of the role of the medial temporal lobes in conscious learning. 1997 marks the discovery of two systems of declarative memory, namely episodic and semantic memories. These major breakthroughs are owed to clinical case studies in neuropsychology. This thesis follows on from the neuropsychological tradition: its genesis owes everything to a patient suffering from an atypical form of developmental amnesia, the patient KA. The starting point of this work was a thorough neuropsychological study of this patient. Two striking findings shortly arose. First, despite lifelong amnesia, KA had acquired exceptional levels of knowledge about the world. Second, remaining explicit learning abilities were restricted to meaningful, not meaningless, memoranda. As a consequence, we have investigated two research pathways in that thesis. First, we aimed at better characterizing preserved learning abilities and brain structure of the patient KA. Second, our goal was to explore how prior knowledge affects new declarative learning or, put simply, how do we learn what we know? In a first series of behavioural and neuroimaging experiments, we have shown in this patient a severe and selective damage of the whole extended hippocampal system, but preserved subhippocampal structures (entorhinal, perirhinal and parahippocampal cortex). The patient suffers from severe episodic amnesia, but we bring striking evidence for supranormal semantic knowledge as well as normal explicit learning skills. These skills were, however, restricted to familiar stimuli, that is, stimuli carrying pre-experimental knowledge. In a second series of behavioural and neuroimaging experiments, we explored the hypothesis that prior knowledge can facilitate new learning in declarative memory, even in aging or in situations where structures of the medial temporal lobe are or injured, as in amnesia or Alzheimer's disease. Our results suggest the existence of processes allowing fast learning in declarative memory, independently of the hippocampal system, and that are sensitive to the presence of pre-existing representations in long-term memory. Such learning processes appear to be selectively affected by Alzheimer's disease at the pre-dementia stage, in relation to a lack of activation of subhippocampal regions. In contrast, healthy elderly were able to rely on these learning processes to compensate for the decline in associative memory associated with aging. This work lends support to the models postulating a functional dissociation with respect to learning in declarative memory. It indeed strengthens recent neurocognitive and computational accounts that suggest a rapid neocortical learning path under certain circumstances. It highlights the dynamics of learning in declarative memory and in particular the fundamental entanglement between "knowing" and "remembering". What I know profoundly impacts what I will remember. The present thesis points towards new cognitive tools for the diagnosis of Alzheimer's disease. It further brings evidence that medial temporal lesions differentially impact learning depending on the status of the memoranda in long-term memory, which sheds a new light on material-specific effects in amnesia. Our work speaks for a thorough consideration of whether the contents of events have prior representations within long-term memory, and to further better characterize their nature if we are to better understand learning mechanisms. It also brings additional clues for a deeper understanding of how learning and memory can be preserved in aging. More generally, it contributes to a better understanding of the factors determining successful learning, with a focus on how retrieval and acquisition processes overlap during learning. Such findings have potential applications in the educational field
Vision périphérique, caractérisation et suppléance de ses fonctions spatiales by Damien Camors( Book )

2 editions published in 2015 in French and held by 2 WorldCat member libraries worldwide

The loss of peripheral vision (tunnel vision) leads to numerous deficits, reducing both independence and quality of life. These deficits reflect spatial cognition impairments, and highlight the close relationship between peripheral vision and spatial representations. This thesis has two main objectives: reaching a better understanding of the nature of these relationships, and using the acquired knowledge in order to propose adaptive, performant and innovative assistive devices able to overcome the peripheral loss. At first, I address the role of peripheral vision in egocentric space coding. I collaborated in a psychophysics experiment, involving detection of visual objects placed in peripheral vision. The visual objects formed similar images on the retina and differed only with respect to their egocentric location: either straight-ahead or eccentric with respect to the head/body midline. We found that straight-ahead objects elicit consistently shorter behavioral responses than eccentric objects. I took in charge a second study evaluating the link between the privileged sensory processing of the straight ahead direction and the dynamic of ocular saccades. Comparison between centripetal and centrifugal pro-saccades and anti-saccades revealed that the superior dynamic of centripetal saccades comes from both sensory and oculomotor factors. These works reveal the early integration of both visual and oculomotor signals in peripheral vision, leading to egocentric representations in which the straight ahead direction is highlighted. Secondly, I investigated the influence of peripheral vision in extracting allocentric spatial representations. In order to assess the role of peripheral vision in allocentric coding, I performed a memory-based pointing task toward previously gazed targets, which were briefly superimposed with visual cues placed at different eccentricities. The results showed that visual cues in peripheral (>10°) vision can contribute to the allocentric coding of a fixated target. A complementary experiment showed that these peripheral allocentric cues play a functional role, notably by facilitating visual searches. These works highlight the importance of peripheral vision in extracting functional spatial relationships between distant elements of the visual environment. Finally, I wanted to promote the development of new assistive devices, able to substitute both egocentric and allocentric spatial functions of the peripheral vision. As a proof of concept, I designed and evaluated a tactile interface mounted on wrist, communicating the spatial location of specific objects and facilitating visual search. Results showed that healthy subjects with artificial tunnel vision (10°) were able to increase by three visual search speeds thank to this tactile interface. Similar results were obtained on a glaucoma subject (field of view 10x15°). My multidisciplinary thesis highlights new roles of peripheral vision in spatial representations and proposes an innovative solution to develop assistive device for tunnel vision
Stratégies d'apprentissage et mémoire à long terme d'associations mot-objet chez le jeune enfant et le chien by Danaé Rémon( Book )

2 editions published in 2019 in English and held by 2 WorldCat member libraries worldwide

All of us occasionally remember information or personal events that occurred a long time ago. But what about young children and distantly related animal species? Do young children and animals also form memories that can last in time? And if so, does memory formation rely on the same principles than those established in human adults? This thesis intended to examine these questions in the context of an associative learning concept involving complex bimodal stimuli: the word-object concept; both in young children and domestic dogs. For these two models, we explored some parameters susceptible to facilitate the encoding and storage of this type of information in memory. In particular, we attempted to determine if the number of presentations of novel word-object associations during learning influenced the retention of the name of these objects after a delay. We also aimed to establish the minimal number of presentations of the pairs required to induce a memory trace. Finally, we examined the efficacy of two learning strategies on the ability to remember the names of novel objects and demonstrated that the efficacy of the strategies implemented in humans evolves during development and seems not to apply to dogs. In brief, our results enlightened some principles underlying the formation of sensory memories in an early-developing brain system as well as in a non-primate species, and allow us to make assumptions about the underlying brain mechanisms
Adéquation algorithme-architecture de réseaux de neurones à spikes pour les architectures matérielles massivement parallèles by Paul Ferré( Book )

2 editions published in 2018 in English and held by 2 WorldCat member libraries worldwide

The last decade has seen the re-emergence of machine learning methods based on formal neural networks under the name of deep learning. Although these methods have enabled a major breakthrough in machine learning, several obstacles to the possibility of industrializing these methods persist, notably the need to collect and label a very large amount of data as well as the computing power necessary to perform learning and inference with this type of neural network. In this thesis, we propose to study the adequacy between inference and learning algorithms derived from biological neural networks and massively parallel hardware architectures. We show with three contribution that such adequacy drastically accelerates computation times inherent to neural networks. In our first axis, we study the adequacy of the BCVision software engine developed by Brainchip SAS for GPU platforms. We also propose the introduction of a coarse-to-fine architecture based on complex cells. We show that GPU portage accelerates processing by a factor of seven, while the coarse-to-fine architecture reaches a factor of one thousand. The second contribution presents three algorithms for spike propagation adapted to parallel architectures. We study exhaustively the computational models of these algorithms, allowing the selection or design of the hardware system adapted to the parameters of the desired network. In our third axis we present a method to apply the Spike-Timing-Dependent-Plasticity rule to image data in order to learn visual representations in an unsupervised manner. We show that our approach allows the effective learning a hierarchy of representations relevant to image classification issues, while requiring ten times less data than other approaches in the literature
Le rôle des oscillations du cerveau dans la perception visuelle, l'attention et la conscience by Canhuang Luo( Book )

2 editions published in 2020 in English and held by 2 WorldCat member libraries worldwide

Oscillations are ubiquitous in the brain. A large body of literature has supported that brain oscillations are not a by-product of brain activities; in fact, they shape our perception by modulating cortical excitability and facilitating neuronal communications. Consequently, our visual perception, attention and maybe even consciousness wax and wane across time. However, the role of oscillations in these perceptual or cognitive functions is not entirely understood. For visual perception and attention, although the relationship between them and brain oscillations has been established, it is unclear where and how these brain oscillations are generated. As for consciousness, how the oscillations are involved in producing conscious perception remains unknown. These are the questions the current thesis attempts to address. The thesis starts with brain oscillations in the most basic and best understood brain function - visual perception. It has been suggested that visual perception is an oscillatory process, sampling the world at the alpha frequency. Perceptual echoes are one demonstration of visual sampling. The echo is an impulse response function that oscillates at ~10 Hz in response to white-noise stimuli. While the temporal properties are gradually revealed, the origin of the echoes remains unclear. The first study set out to study the neural basis of perceptual echoes, and we found the echoes originate in the early visual cortex. Next, we move on to attention. It has been shown that attention samples the environment at theta frequency. A monkey study suggests that the theta oscillation of attention may arise from competitive receptive field interactions of V4. To investigate if the mechanism can be generalized to humans, we replicate the behavioral experiment in humans. Finally, in the last two studies, we examine brain oscillations in consciousness. Utilizing binocular rivalry, we first investigate if the perceptual echoes require consciousness. The results show that perceptual echoes can be elicited both when the stimulus is in consciousness and out of consciousness. Second, we investigate information flow during binocular rivalry and show an increased top-down beta and theta activities before perceptual switches. In conclusion, the brain is a dynamic system in which the oscillations flexibly facilitate various brain functions by playing different functional roles
Amélioration de la fonctionnalité visuelle par l'utilisation concomitante de l'apprentissage perceptif et de la stimulation cérébrale : le cas de la dégénérescence maculaire by Giulio Contemori( Book )

2 editions published in 2020 in English and held by 2 WorldCat member libraries worldwide

Macular degeneration (MD) is a common visual disorder in the aging population characterized by a loss of central vision, reduced visual acuity contrast sensitivity, and increased crowding. This impairment strongly affects the quality of life and personal autonomy. There is currently no cure for AMD, available treatment options are only able to slow down the disease, and even palliative treatments are rare. After the emergence of the central scotoma, patients with MD develop one or more eccentric fixation areas - preferred retinal loci (PRLs) - that are used for fixation, reading, tracking, and other visual tasks that require finer ocular abilities. The final goal of the project was to investigate and to improve the residual visual abilities in the PRL. Four studies were conducted in total. Study 1 was conducted in MD patients to investigate whether after the emergence of the scotoma, the PRL acquire enhanced abilities in the processing of the visual information through spontaneous or use-dependent adaptive plasticity. Study 2 aimed to assess the effects of a single administration of transcranial random noise electrical stimulation (tRNS), a subtype of non-invasive transcranial electrical stimulation, on the spatial integration in the healthy visual cortex. Study 3 aimed to assess the between session effect of daily repeated tRNS coupled with perceptual training. The objective of study 4 was to translate the previous findings into a clinically applicable treatment approach by combining tRNS and perceptual training in adult patients with MD. Contrary to previous results, we found neither a phenomenon of spontaneous nor use-dependent cortical plasticity undergoing in the PRL before the training. We also found that the tRNS was able to modulate the visuospatial integration in the early visual processing, promoting plastic changes in the stimulated network. Its effects were not limited to the short-term modulation but also produced a boosting of the learning in a crowding task. The final experiment showed that a combination of tRNS and perceptual training could result in greater improvements and larger transfer to untrained visual tasks in adults with MD than training alone. Overall, our results indicate that tRNS of the visual cortex has potential application as an additional therapy to improve vision in adults with bilateral central blindness
Usage de la connectivité pour étudier les (dys)fonctions cérébrales by Jakub Kopal( Book )

2 editions published in 2021 in English and held by 2 WorldCat member libraries worldwide

We picture the brain as a complex network of structurally connected regions that are functionally coupled. Brain functions arise from the coordinated activity of distant cortical regions. Connectivity is used to represent the cooperation of segregated and functionally specialized brain regions. Whether it is the analysis of anatomical links, statistical dependencies, or causal interactions, connectivity reveals fundamental aspects of brain (dys)function. However, estimating and applying connectivity still faces many challenges; therefore, this work is devoted to tackling them. The first challenge stems from the detrimental effect of systematic noise (such as head movements) on connectivity estimates. We proposed an index that depicts connectivity quality and can reflect various artifacts, processing errors, and brain pathology, allowing extensive use in data quality screening and methodological investigations. Furthermore, connectivity alterations play an invaluable role in understanding brain dysfunction. Investigating the mechanisms of epilepsy, we show that connectivity can track gradual changes of seizure susceptibility and identify driving factors of seizure generation. Identifying critical times of connectivity changes could help in successful seizure prediction. Finally, how the brain adapts to task demands on fast timescales is not well understood. We present a combination of intracranial EEG and state-of-art measures to investigate network dynamics during recognition memory. Understanding how the brain dynamically faces rapid changes in cognitive demands is vital to our comprehension of the neural basis of cognition. In conclusion, the modest goal of this thesis is to at least partially answer some of the many challenges that current neuroscience is facing
Étude de la relation causale entre les oscillations cérébrales et la perception en utilisant des techniques non invasives de stimulation cérébrale by Samson Chota( Book )

2 editions published in 2020 in English and held by 2 WorldCat member libraries worldwide

It should have become clear now that oscillatory activity has profound effects on multiple aspects of our perception and is strongly involved in the way we sample our visual environment. Many of these relationships however are poorly understood, specifically in their causal-directional nature. In this thesis, I investigate the causal role of neural oscillations in temporal sampling mechanisms. The original manuscripts in chapter II and III are dedicated to perceptual sampling in the alpha band. It is hypothesized that this form of sampling has effects on time perception in our visual system. We tested this by manipulating alpha oscillations with rhythmic stimulation while observing changes in perceived relative timing of visual stimuli. Besides behavioral oscillations there are also neural signatures that hint at the intrinsic periodicity with which sensory cortices collect information. The oscillatory nature of perceptual echoes strongly implies that the visual system selectively reverbrates the 10 Hz component of its input. If we could extend these perceptual echoes to other modalities we would have evidence that 1. these other modalities also process information periodically and 2. that they utilize similar neural mechanisms for this purpose. In the original manuscripts in chapter IV I investigated if we can find perceptual echoes in the tactile domain. The periodic sampling mechanisms of the brain seem to be dissociable into a more low-level perceptual and a more high-level attentional sampling mechanism. Attentional sampling is assumed to be more flexible, task dependent and has recently been hypothesized to be caused by theta rhythmic activity in macaques. Providing support for these findings in humans would help us to identify the oscillatory mechanism that is responsible for behavioral attentional fluctuations found in many studies. The original manuscript in chapter V presents a study in which we replicate behavioral findings of the macaque-study in humans. Which location in the visual field attentional sampling mechanisms can collect information from depends entirely on the position of our eyes. Saccades and attentional sampling need therefore be highly coordinated. One way to synchronize these two systems is through oscillatory activity. It has been proposed that saccades, and surprisingly also strong visual transients, can reset the phase of theta oscillations which in turn allow for well timed processing of relevant stimuli. If this mechanism indeed relies on rhythmic activity then we should be able to disrupt it and observe corresponding errors in attentional sampling. The original manuscript in chapter VI investigates which effects strong visual disruptions have on the perceived relative timing of two stimuli. During my doctorate I sought to answer the following research questions: 1. Is the occipital alpha rhythm causally involved in discretely sampling visual information? (chapter II and III) 2. Is there a link between oscillatory activity and rhythmic sampling in the somatosensory system? (chapter IV) 3. Can we manipulate theta rhythmic activity to modulate attentional sampling? (chapter V and VI)
Mismatch negativity, un marqueur neuronal de la plasticité spatiale auditive chez les sujets sourds unilatéraux by Mariam Alzaher( Book )

2 editions published in 2020 in English and held by 2 WorldCat member libraries worldwide

This thesis investigates different spatial hearing functions in 3 types of populations: Normal Hearing Subjects (NHS), Unilateral Hearing Loss patients (UHL) and Bilateral Hearing Loss patients ( BHL). To discover the mechanisms underlying the adaptive strategies that are observed in UHL with acquired deafness. The main aim of the thesis is to verify whether spatial Mismatch Negativity (MMN) could be a neuronal marker of spatial auditory plasticity observed in UHL patients, and to verify whether these neural correlates are consistent with the spatial auditory performance. Two types of investigations were applied to 20 NHS, 21 UHL and 14 BHL. The first investigation is a sound source identification task measured by the root mean square error (RMS). The second assessment is an electroencephalography (EEG) study where we analyzed the amplitude and latency of the MMN. MMN is defined as an auditory evoked potential that reflects the brain's ability to detect a change in one physical property of a sound. We used a standard sound in a reference position (50°) with three deviations from the standard (10° , 20°, and 100°), in binaural and monaural conditions. UHL patients were divided into 3 groups according to their spatial performances. The group of good performers (UHL {low rms}) showed better RMS scores in comparison with NHS with earplugs (NHS-mon), with performances similar to those of NHS subjects in binaural condition. A progressive increase of the MMN with the angle of deviation from the standard was noted in all groups. With a significant reduction of MMN amplitude in monaural NHS when the ear plug was applied on the ipsilateral side of the standard. MMN showed consistent variation with the behavioral observations, where UHL {low rms} patients had larger MMN amplitudes than those of monaural NHS and similar to those of binaural NHS. UHL patients have adaptive spatial auditory strategies. Our study was able to demonstrate that spatial auditory plasticity that occurs after deafness can be reflected by the MMN. Neural observations (i.e. the MMN) are correlated with behavioral observations of spatial source identification. This means that the spatial cortical plasticity, that took place in these subjects, is not limited to the functions of identification of the sound source, but exceeds these capacities towards more complex mechanisms such as deviance detection and short-term memory, that are involved in the spatial discrimination function
Codage cortical de la synesthésie graphème-couleur by Mathieu Ruiz( )

1 edition published in 2014 in French and held by 2 WorldCat member libraries worldwide

Synesthesia is a fascinating phenomenon that offers the opportunity to study the neural bases of subjective experiences in healthy subjects. Grapheme-color synesthetes (1 to 5 % of the population - who do not know it most of the time) arbitrarily and systematically associate a specific color to letters or digits. This PhD thesis work focuses on this type of synesthesia and explores whether common neural networks are involved both in 'real' color perception and synesthetic color experience. In a previous study from the host team using functional Magnetic Resonance Imaging (MRI), no implication of 'color areas' where found (Hupé et al., 2012). A standard (univariate) statistical analysis of the data processing was used.This PhD thesis aims at determining if synesthetic colors involve real color neural networks with the use of a multivariate statistical technique (Multivoxel Pattern Analysis - MVPA). Unlike univariate analysis it uses sets of voxels (the pixels in 3D forming the images) and take into account their patterns of activation linked to the encoding of specific information in the brain. This encoding is performed at the neuronal level and fMRI indirectly and non-invasively quantifies it through hemodynamic variations induced by the neuronal activity. MVPA is a particularly adapted approach to measure fine grained and distributed information encoding. The goal of the thesis is to explore its efficiency for the study of grapheme-color synesthesia for which standard analyses failed. In practice, it requires the use of specific protocols, mastering numerous parameters influencing the results and the joint use of univariate analysis. In the first step of this thesis, we evaluated different methodological aspects to optimize the processing chain in order to obtain robust and reliable results.Then, we compared the neural processing of real colors and synesthetic colors in 2 groups of synesthetes (n=20) and non synesthetes (n=20). We found that synesthetic colors processing does not share common neural networks with real color processing. This suggests that the neural bases of synesthetic colors are not localized in the retinotopic visual areas or in the visual expertise areas (the 'ventral pathway' areas). This may also suggest that, although those areas are involved, different neural networks are implicated in real color and synesthetic color perception. These results raise the question of the limits of the interpretation of the signal measured by fMRI, indirectly linked to the neuronal activity. The identification of the neural networks involved in the subjective experience of synesthetic colors remains an open issue
Validation d'une nouvelle électrode hybride intracérébrale comportant des tétrodes dans l'épilepsie pharmaco-résistante by Elodie Despouy( Book )

2 editions published in 2019 in French and held by 2 WorldCat member libraries worldwide

This thesis was done in collaboration with DIXI medical, the CHU of Toulouse and the Centre de Recherche Cerveau et Cognition in order to validate the use of a new hybrid electrode in drug refractory epileptic patients. These electrodes are used in order to identify the seizure onset zone during stereo-electroencephalography. If this zone can be identified and removed, drug-refractory epileptic patients may become seizure free. In recent years, epilepsy research has focused on high frequency oscillations and more precisely on fast-ripples (200-600 Hz). These oscillations appear to be a good biomarker of the seizure onset zone. Fast-ripples can be detected with clinical macroelectrodes (diameter 800-1300 µm) but their identification is facilitated with microelectrodes (diameter 80 µm). In the CHU of Toulouse, clinical macroelectrodes have a diameter of 800 µm and hybrid electrodes (combining macro and microelectrodes) available on the market have a diameter of 1300 µm. This problem leads to a collaboration with DIXI medical in order to manufacture a new hybrid electrode with the same diameter as the clinical ones. The new hybrid electrode has different advantages: (1) the microelectrodes are, for the first time in the human, in a tetrode configuration (4 microwires bundled together), which facilitates single neuron identification; (2) microelectrodes can be extended up to 2 mm, which enable to search for neurons; (3) microelectrodes can be extended between the macrocontacts, which enable multiscale analysis. This new hybrid electrode is under clinical investigation in the CHU of Toulouse since March 2015. The goal of my thesis is to demonstrate the safety of the electrode and its ability to record EEG signal of interest both in epilepsy and in fundamental research. My thesis is composed of a literature review and 5 studies. The first study is a methodological study, which present the characteristics of the new hybrid electrode and demonstrates its safety. Studies 2, 3 and 4 concern the use of the hybrid electrode in epilepsy. More precisely, the 2nd study describes the case of a patient with a tuberous sclerosis lesion associated with drug-refractory epilepsy. It's the first time that neuronal activity can be recorded and analyzed in vivo in this pathology. The 3rd study is required to CE mark the new electrode. In this study, we verify whether the fast-ripples recorded with the new hybrid electrodes are really a good biomarker of the seizure onset zone. The 4th study is about the neurophysiopathology of fast-ripples. We analyze the relationship between neuronal activities and fast-ripples. Finally, the 5th study describe the spatiotemporal dynamic of visual recognition memory using macro-electrodes. It is a preliminary study to the analyses of neuronal activity during such cognitive task
Étude de l'activité neuro-oscillatoire thêta en tant que marqueur développemental dans l'évaluation d'un entraînement écologique du contrôle cognitif chez l'enfant by Nicolas Adam( Book )

2 editions published in 2020 in French and held by 2 WorldCat member libraries worldwide

In this thesis, we test the hypothesis that through the self-regulation implemented during the pretend play, it is possible to train the processes of cognitive control processing and thus accelerate its development. This thesis integrates an original approach aimed at understanding the effects of age and the effects of training on the same cognitive and cognitive measures of cognitive control. We are interested in highlighting behavioral and electrophysiological markers of the development of cognitive control through a conflict task in school and preschool children. We then use these markers with preschool children to characterize the effects of ecological cognitive control training using the same assessment task. We have demonstrated that through a conflict management task with different levels of interference, the amplitude of theta neuro-oscillatory activity allowed to characterize the control engagement dynamics as well as the intensity of the generated conflict. In addition, the latency of this activity provides information on the maturation of the underlying networks. These results also underline the interest of understanding cognitive control through interference management to characterize finely the processing treatment underlying its implementation. The performances suggest an improvement of the processes of treatment of the cognitive control with the age both at the behavioral and neuronal level. Older children seem to be better able to implement conflict management and monitoring skills. On the other hand, the results observed during the second evaluation in preschool children suggest an adaptation in the implementation of the control. Training improves the maturity of pretend play skills. However, more general measures of cognitive control or self-regulation show no benefit for the experimental group compared to the control group. Finally, our results enrich current knowledge on conflict management in childhood
Ectonucléotidases, adénosine et transmission synaptique by Marie Gleizes( Book )

2 editions published in 2017 in French and held by 2 WorldCat member libraries worldwide

Dans le cerveau, les fonctions de la phosphatase alcaline non spécifique des tissus (TNAP) ne sont pas clairement identifiées. La localisation et l'expression de cette enzyme au niveau neuronal suggère cependant, qu'elle joue un rôle important dans le développement et le fonctionnement du cerveau. Cela est supporté par la présence de graves crises d'épilepsie chez les humains porteurs d'une mutation de la TNAP. Ces crises d'épilepsie sont létales chez les souris KO pour la TNAP. Des études chez la souris montrent que la TNAP pourrait réguler l'inhibition postsynaptique médiée par le GABA et elle pourrait être impliquée dans l'inhibition présynaptique médiée par l'adénosine. L'adénosine est, en partie, synthétisée via la déphosphorylation successive de l'ATP en ADP puis en AMP par des ectonucléotidases. Parmi elles, la TNAP et l'ecto- 5'-nucléotidase (NT5E) catalysent l'hydrolyse de l'AMP en adénosine dans le cortex cérébral. L'adénosine agit principalement au niveau présynaptique par l'intermédiaire des récepteurs A1. Ainsi l'adénosine a une influence sur la transmission synaptique et sur la plasticité synaptique. Ceci pourrait expliquer, en partie, les crises d'épilepsie observées chez les souris KO pour la TNAP. Les deux objectifs principaux de ma thèse ont été : (1) évaluer la contribution de la TNAP dans la production d'adénosine dans le cerveau ; (2) étudier l'influence de l'adénosine sur la plasticité synaptique. Premièrement, l'étude de la contribution de la TNAP dans la production d'adénosine dans le cerveau a été réalisée au moyen de deux approches complémentaires. Une approche métabolomique (spectroscopie RMN du proton) sur des cerveaux entiers de souris KO pour la TNAP a permis de montrer que la TNAP participe, entre autre, à la synthèse d'adénosine dans le cerveau. Une deuxième approche, électrophysiologique sur tranches de cerveaux de souris in vitro, nous permet d'examiner les conséquences de l'inhibition des ectonucléotidases intervenant dans la synthèse de l'adénosine. Elle a révélé que l'inhibition des ectonucléotidases (TNAP et NT5E) ne supprime pas l'effet inhibiteur de l'AMP médiée par les récepteurs A1. Deuxièmement, nous avons étudié l'influence de l'adénosine sur la plasticité synaptique à courte terme. Nous avons enregistré des potentiels de champs dans la couche Ia du cortex piriforme en réponse à des stimulations électriques (3,125 à 100 Hz) présentée avec des fréquences recouvrant la gamme d'oscillations physiologiques. Nos résultats montrent qu'avec de fortes concentrations d'adénosine, la facilitation est accentuée par rapport à celle observée en situation contrôle. Cet effet est observé pour des fréquences supérieures ou égales à 25 Hz. De plus, cette accentuation est d'autant plus grande que la fréquence est élevée (maximum atteint à 100 Hz pour 100 µM). En bloquant l'action de l'adénosine endogène, l'effet contraire est observé : une facilitation déficitaire par rapport au contrôle et dont le défaut est croissant avec la fréquence de stimulation. Tous ces résultats convergent vers l'hypothèse qu'une déficience en TNAP, traduite par une absence d'adénosine, pourrait contribuer au maintien des processus épileptiques générés par un déséquilibre de l'inhibition et de l'excitation dû à une diminution de GABA. L'effet inhibiteur de l'AMP médié par les récepteurs A1 ne serait pas suffisant pour contrecarrer les crises d'épilepsie observées chez les sujets hypophosphatasiques et les souris KO pour la TNAP
Traitement des signaux de communication dans le syndrome de Prader-Willi : aspects descriptifs, analytiques et évolutifs by Jimmy Debladis( Book )

2 editions published in 2019 in French and held by 2 WorldCat member libraries worldwide

Le syndrome de Prader-Willi (SPW) est un syndrome génétique rare qui touche 1 naissance sur 20 000 en France dont les deux origines génétiques les plus fréquentes sont la délétion de la région 15q11q12 du chromosome 15 paternel et la disomie maternelle. Ce syndrome est marqué par une hypotonie néonatale, puis au cours du développement, apparaissent l'hyperphagie, les troubles de la satiété et des troubles comportementaux. Sur le plan social, ces patients ont des interactions sociales atypiques, faisant référence à celles décrites dans les troubles du spectre de l'autisme (TSA). Dans le SPW, les données concernant les troubles du comportement et les troubles des interactions sociales sont rares. Il est détaillé que ces patients ont des déficits de reconnaissance des émotions et des signatures cérébrales en réponse aux visages atypiques. Néanmoins, beaucoup de processus de traitement des signaux sociaux restent encore inexplorés. Cette thèse permet d'apporter de nouvelles données sur les processus de traitement des voix et des visages qui pourraient être altérés dans le SPW. Nous avons développé un ensemble complet de tests comportementaux simples qui visent à étudier le traitement des voix et des visages. Nous avons démontré que les patients avec un SPW avaient une lenteur motrice et perceptive. De plus, nous relevons un déficit de traitement des visages, mais qui n'est pas généralisable aux voix. Selon nous, les déficits présents sur le traitement des visages, pourraient provenir d'un trouble dans la perception globale et dans l'unification de plusieurs sources d'informations entre elles, faisant référence à la cohérence centrale. Enfin, nous avons montré que globalement, les patients avec une disomie souffrent de troubles sociaux plus sévères que les patients avec une délétion. Par ailleurs, un versant thérapeutique est développé avec l'administration d'ocytocine (OT) chez les enfants et les adultes avec un SPW. L'OT a, au cours des dernières années, fait l'objet d'un vif intérêt pour les populations ayant des troubles des interactions sociales. Ce versant thérapeutique permettra d'étudier les effets à long terme de l'OT sur des enfants et les potentiels bénéfices d'un traitement sur les comportements alimentaires et sociaux
Predictive coding : its spike-time based neuronal implementation and its relationship with perception and oscillations by Biao Han( Book )

2 editions published in 2016 in English and held by 2 WorldCat member libraries worldwide

Dans cette thèse, nous avons étudié le codage prédictif and sa relation avec la perception et les oscillations. Nous avons, dans l'introduction, fait une revue des connaissances sur les neurones et le néocortex et un état de l'art du codage prédictif. Dans les chapitres principaux, nous avons tout d'abord, proposé l'idée, au travers d'une étude théorique, que la temporalité de la décharge crée une inhibition sélective dans les réseaux excitateurs non-sélectifs rétroactifs. Ensuite, nous avons montré les effets perceptuels du codage prédictif: la perception de la forme améliore la perception du contraste. Enfin, nous avons montré que le codage prédictif peut utiliser des oscillations dans différentes bandes de fréquences pour transmettre les informations en avant et en rétroaction. Cette thèse a fourni un mécanisme neuronal viable et innovant pour le codage prédictif soutenu par des données empiriques démontrant des prédictions rétroactives excitatrices et une relation forte entre codage prédictif et oscillations
Flexibilité temporelle et spatiale des représentations neurales d'objets visuels lors d'apprentissages by Medhi Senoussi( Book )

2 editions published in 2016 in English and held by 2 WorldCat member libraries worldwide

The work presented in this thesis deals with the effect of short- and long-term learning on the visual system. We first demonstrated through electroencephalographic recordings that learning a sequence of visual stimuli induced spontaneous and selective cerebral activity to the next-to-appear stimulus and that this selective activity was expressed in the alpha and beta bands of cerebral electrical activity. Subsequently, we showed through functional magnetic resonance imaging that during long learning (three weeks) the neural representations of associated visual categories were modulated and became more similar due to learning. The work presented in this thesis has thus made it possible to better characterize the impact of learning at different time scales on the neural representations of visual objects
Compléxité de l'intégration multisensorielle chez le primate humain et non-humain : du comportement à l'électrophysiologie corticale et sous-corticale by Cécile Juan( Book )

2 editions published in 2017 in French and held by 2 WorldCat member libraries worldwide

Dans notre environnement, nous sommes constamment exposés à de multiples stimuli sensoriels que notre cerveau doit analyser. Afin d'interagir avec le monde qui nous entoure, nous devons intégrer ces différentes sources d'informations sensorielles. L'étude des processus d'intégration multisensorielle est essentielle pour comprendre comment le cerveau intègre les éléments séparés d'un objet défini par plusieurs composantes sensorielles pour former un percept unifié. Il est maintenant couramment admis que la présentation conjointe de plusieurs informations sensorielles de modalités différentes d'un même stimulus peut faciliter la perception. Cette facilitation multisensorielle semble être soumise à des règles particulières puisque certains facteurs l'influencent. Parmi eux, nous avons étudié, dans notre première étude, l'impact de trois facteurs que sont la saillance, la congruence sémantique et le changement de modalité sur les performances de détection de stimuli naturels chez l'homme et le singe. L'utilisation de stimuli naturels nous a permis de mettre en lumière l'influence des paramètres physiques des stimuli sur l'intégration multisensorielle. De plus, nous avons montré que les effets de ces facteurs sur des stimuli naturels diffèrent de ceux retrouvés avec des stimuli simples. Ces résultats convergent vers des effets multifactoriels sur la facilitation multisensorielle dont la force, les interdépendances et l'ordre varieraient en fonction de la tâche comportementale et de ce fait, de la charge cognitive. D'un point de vue anatomique et plus précisément au niveau cortical, les processus d'intégration multisensorielle paraissaient être jusqu'à récemment une caractéristique que seules possédaient les aires associatives situées au sommet de la hiérarchie du traitement de l'information. On sait maintenant que des aires corticales de bas niveau, pensées jusque-là comme étant unisensorielles, sont impliquées dans les processus multisensoriels, soulevant ainsi la question des aires sous-corticales. Des études anatomiques ont mis en évidence l'existence de noyaux thalamiques qui, par leurs connexions, pourraient permettre un transfert rapide et même une intégration des informations sensorielles. Cette nouvelle littérature témoigne de la grande complexité des réseaux cérébraux de la multisensorialité. Dans deux études électrophysiologiques chez le singe, nous avons examiné les propriétés multisensorielles de deux structures, le gyrus cingulaire postérieur et le pulvinar médian, qui n'avaient jamais été explorées auparavant dans un contexte multisensoriel. Nous avons montré que ces structures sont non seulement multisensorielles mais également intégratives et qu'elles pourraient appartenir à un même système fonctionnel. Ces travaux de thèse ont apporté des éléments supplémentaires quant à notre compréhension des processus d'intégration multisensorielle au niveau comportemental et des réseaux cérébraux sous-jacents et particulièrement ceux liés à l'intégration de stimuli naturels
Bringing very long term memories back to life by Christelle Larzabal( Book )

2 editions published in 2017 in English and held by 2 WorldCat member libraries worldwide

On pense souvent que notre mémoire nous joue des tours et nous fait défaut. Ces oublis concernent généralement des souvenirs qui ne sont pourtant pas si vieux. Alors quand il s'agit de se rappeler d'informations sensorielles auxquelles nous n'avons pas repensé depuis plusieurs dizaines d'années, pas de doute, il ne reste plus rien... Mais en est-on vraiment sûr? Et si l'information était toujours là, prête à se manifester de manière explicite -comme sous forme de rappel ou de sentiment de familiarité- pour peu que les conditions le lui permettent? A ce jour, très peu d'expériences ont été menées sur ce sujet. L'objectif de ma thèse a donc été d'apporter des premiers éléments de réponse concernant la récupération de mémoires laissées inactives. Ma recherche s'est orientée selon deux axes principaux : une première partie théorique où je montre a) qu'il n'est pas nécessaire de réactiver une trace mnésique pour la maintenir à très long-terme si elle a été suffisamment répétée et b) que la récupération explicite de cette mémoire serait possible grâce à la présentation d'informations qui cibleraient au mieux le souvenir ; une seconde partie expérimentale où je montre a) que des participants sont capables de récupérer de manière explicite des informations laissées en dormance pendant au moins une dizaine d'années et b) que cette trace mnésique pourrait être détectée sur des tracés d'Electroencéphalographie (EEG). Ainsi, et aussi étonnant que cela puisse paraître, dans des conditions favorables à leur réactivation, d'anciennes traces mnésiques que l'on croyait disparues, peuvent de nouveau surgir sous la manifestation de rappel ou de sentiment de familiarité par exemple. Ces résultats soulèvent des questions majeures concernant le stockage neuronal de cette information
 
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Alternative Names
Brain and Cognition Research Center facility in Toulouse, France

Brain and Cognition Research Centre

Centre de rechercher Cerveau & cognition

Centre national de la recherche scientifique

CerCo

CerCO. Université de Toulouse. France

CNRS CERCO UMR 5549. Université de Toulouse. France

Ecole des hautes études en sciences sociales

UMR 5549

UMR5549

Université Paul-Sabatier

Languages
English (24)

French (15)